ABC News’ Devin Dwyer reports: Pop star and gay rights advocate Lady Gaga is taking her campaign to repeal the military’s Don’t Ask Don’t Tell policy to the doorstep of two senators whom activists believe could cast key votes in an attempt to override an expected filibuster of the measure. Gaga will speak a rally in Portland, Maine, this afternoon in conjunction with the Service Members Legal Defense Network, a gay and lesbian advocacy group. A vote on the National Defense Authorization Act, which includes a repeal of the controversial military policy, is expected tomorrow. “The votes to break McCain’s filibuster are not there. We need [Maine Republican] Sens. [Olympia] Snowe and [Susan] Collins on board; they’re key to us breaking the filibuster,” said Aubrey Sarvis, an Army veteran and executive director for Servicemembers Legal Defense Network. “We’re bringing gay and straight service members to Portland to help make the case. And we’re proud to have the support of Lady Gaga to bring grassroots attention to repeal at a critical hour.” Gaga, who has more than 6 million followers on Twitter, has been trying to leverage her fans to lobby for an end to DADT. On Friday she released a YouTube video , which has received more than 1 million views and in which she calls a filibuster “shameless” and asks supporters to call their members of Congress.